When asked how old she was, the teacher replied: My age in years is
not prime but odd and when reversed and added to my age you have a
Can you work out how many of each kind of pencil this student
A combination mechanism for a safe comprises thirty-two tumblers
numbered from one to thirty-two in such a way that the numbers in
each wheel total 132... Could you open the safe?
To facilitate the ease of obtaining accurate results it would be
useful to have calculators available for the children, particularly
for the later extension ideas.
Children tackling this investigation will be:
It may be worth working through a few examples of the
double-digit problem with the whole class so that the children get
a feel for the procedure. Having done this, they are bound to start
making their own predictions.
Before leaving them to investigate for themselves, it may be
useful to talk about how they are going to record their results.
This becomes particularly important when they come to tackle the
three-digit extension suggested at the end. For those who reach
this stage, a discussion about how to write down the six different
triple-digit numbers systematically may prove valuable.
As usual, encourage children to talk to each other about their
theories, helping them to express these clearly. Bring the class
together as appropriate to share their findings and possible
The pupils themselves will come up with further variations to
investigate so you can take on board their suggestions too.